Very similar to the dual effect in that you film the same scene twice. Once with the ghost and the second time with the car, etc. Walking through the wall is trickier, if you want that you might be best putting the ghost in front of a greenscreen.

What might be intersting is to cover a door or whole in the wall with butcher paper or something and paint it like the wall. Then when you film the normal scene the room has no door. Then you can have the ghost actually rip their way through the wall but the wall remains as far as the normal layer is concerned.

Might be different, more violent, than the standard slip through the wall effortlessly. It does crush any story ideas of the ghost not knowing their a ghost though.

RJSchwarz
San Diego, CA

it would be quite easy to do on a greenscreen.

H.A.